In a Code Division Multiple Access (CDMA) mobile communication system, signals of multiple users are overlapped in the time and frequency domains, and the signals of the respective users upon reception have to be separated from each other with a signal separation method in the digital domain. In the case of co-frequency networking, there is serious multiple-access interference and intersymbol interference, and there is also relatively strong mutual interference between signals of co-frequency neighbor cells. In the prior art, a joint detection technology is used to eliminate the multiple-access interference and the intersymbol interference, in which the co-frequency interference is treated simply as part of background noise.
For a slot CDMA system using array antennas, since information provided from an interference signals of a co-frequency neighbor cell is not available, the co-frequency interference is treated simply as part of the background noise, thus a Direction-of-Arrival (DOA) estimation only for the local cell, i.e. a DOA estimation for a single cell at a single base station, can be performed, and DOA estimations for multiple co-frequency cells at a single base station can not be performed.